I would recommend running the floors underneath all the cabinets.

If the GC wants to do it the other way, make sure the cabinets are installed on a substrate like plywood that is even with the finished floor at the very least.

If the cabinets are installed on the subfloor they will end up slightly lower than desired and also "trapped" by the finished floor.

ditto.

but, more "FYI" in case you need it when talking to your guys:
1/. you haven't said whether your cabs are on "feet" or not. Feet are height adjustable. This is not just a detail; it determines the arguments you will use to say what you want to say.
2/. regardless of that, if anyone does install cabs onto a subfloor (and yes this has been done in millions of homes) it is wise to raise the floor level under the cabs so that it ends up at the same level as the real floor. Dishwashers sliding in and out are one good reason why.
3/. Same thing for tiled floors: it is not a good idea to tile only up to the cabs and then stop, and it IS a good idea to tile beyond the front line of the cabinets, under the cabinets, so that the dishwasher's front two feet stand completely on tiles that are level with the tiles of the floor. The single back foot of the dishwasher is height adjustable too ; therefore one might make a reasonable argument to tile only a few inches and not to tile up to the wall (or not to install a full floor up to the wall).

A flat piece of wood can be tossed down and called a filler or a leveler, without even gluing it onto the subfloor.

4/. the more you cover the subfloor the more you stop noise(s) from traveling through = useful and good to know about, if you have a basement. But it needs to be a continuous cover; think of a plastic bag or saran wrap. Ditto if you want to be sure that bugs and creepy crawlies will have (almost) no access.

I can tell you what we are doing.

After framing/rough plumbing & electrical/sheetrock/etc, our GC put in the plywood subfloor, then put down the hardwood floor, then put down a sealer coat of poly under where all of the cabinets would go, and then installed the cabinets. This should help protect the wood somewhat against spills/leaks/etc under the cabinets and appliances.

When everything is done, he will sand the floor right up to the edge of the cabinets and finish the floor properly.

I thought he would have held off on installing toe kicks and end panels until after the floor was fully finished, but he said that was not necessary -- they will sand right up to the cabinets without marking them at all. I hope he's right :)

In the kitchen that we ripped out, a tile floor had been put down on top of a vinyl floor as part of the previous owner's kitchen 'refresh'. This trapped the DW under the cabinet... it would have been fun to replace it. Whatever you do, make sure you don't do *that*!

OK - there is some very good advice here, and plenty of helpful comments. I am going to make sure that some sort of plywood of the proper height to match the wood floor is installed under the base cab locations, and it will extend to the drywall. Thank you, palimpest, circuspeanut, davidro1, and NYSteve.
I honestly think it would have better to just install the hardwood first, including under the cabs, but whatever. No big deal, I guess. Plus it did save me a bit of money because I ordered less wood this way.
Thanks everyone.

Ours were installed right on the subfloor. They were frameless and came without a base. They build the base supports the right height to make the counter height 36" above the floor (taking into account the counter thickness as well as the floor thickness). The toe kicks went in front of that. I don't see any problem with placing directly on the sub floor if it is flat and they have the ability to make them the right height with a base or adjustable legs.

the only way I can think that NYSteve's kitchen floor sanding will look good is if a piece of trim is added after the fact, to hide the visible line left over after the sanding operation is done. There is no way to sand "up to" anything. A line of unsanded material is always left over. Adding trim thickens the toekick material, and makes the toekick less useable as intended as a toe kick.

".... he will sand the floor right up to the edge of the cabinets and finish the floor properly....." = whatever that means!!?!

If NYSteve's GC simply sands the floor an inch or two beyond the base cabinets, there's no need to re-sand it when the main area of the floor is done. A pass with the screen will blend in the edge/kick zone.
It's a thoughtful approach.
Casey

It it's real hardwood that could conceivably be in place for many years, I too would be more comfortable with the cupboard installation on top of the hardwood. In spite of our best intentions and designs, there may come a time when you may desire a different kitchen design/layout. It's always a pleasant surprise when you renovate a property and find that an installation was done over the floor, as matching a stain or finish is always an easier job than doing a floor repair.

Our contractor ran the floor under the cabinets. I preferred the appproach for future flexibility, ease of access to dishwasher, etc. and, of course, having the option to rip the kitchen out and use it as a dance floor!

Here's the post-floor, pre cabinet picture:
{{!gwi}}

Good luck!

We tiled under the front of the cabinets several inches and then used plywood strips under the edges of the cabinets so that everything was level.

Davidro1: I had the same concern. He says he does it this way all the time (putting unfinished floor down and then finishing after cabinet install). His flooring sub has a great reputation... Even if he has to sand around the cabinet edges by hand, I have a feeling they will do what is necessary to minimize the "line." In most places, that line would be at the toe-kick and completely hidden anyhow. It's only against the end panels where there is even a concern, and I assume with some care and craftsmanship, it will be hard or impossible to see. At least that's what I'm hoping at this point!

Isn't this the same problem as refinishing a floor when the baseboard is already down, however?

My floor guys finished the hardwood floors after my cabs were in. They did a great job and kept my cabs totally clean. the toekick and shoe molding for the cabinets went on after, my you couldn't see a "line" of any sort where the finish stopped short of the cabinets. it looks great.

Our recommendation by an extremely reputable hardwood flooring guy was to lay the hardwoods in the kitchen and then do two of the three coats of stain (which means some sanding is required) and after two coats, put the cabinets in and then finish off the floors. This is his preference bc we have a softer hardwood, walnut, and this would help protect the floors during the cabinet install and they could sand out any problems after the install and give us a truly finished look. Also, by coating twice before the install it protects the wood from any future water problems since the wood is sealed. Just how we are doing it...

We looked under the original cabs in our house and the hardwoods did go underneath. The hardwoods underneath were unfinished so they installed the cabs over them and then finished the floors after. I would have preferred they been stained first but we didn't build the house. Kind of hoping we could replace a counter run with an island for better flow but that would mean refinishing the entire first floor hardwood floors.

Our recommendation by an extremely reputable hardwood flooring guy was to lay the hardwoods in the kitchen and then do two of the three coats of stain (which means some sanding is required) and after two coats, put the cabinets in and then finish off the floors.

That is what our contractor did as well.

Ditto to Sas. My guy does the same thing. He says he's the last one out of a reno house.

My guy did it like NYSteve's did. No lines. FWIW.

We installed our own oak floor. Having the whole bare room to work in wall to wall was wonderful. Although there is "waste" by putting oak under the cabs, it's less wasteful of the workpersons' time and the cost of the rental gear--no need to do fancy fitting. Plus we put the (inevitable) shabby or irregular boards under the future cabinet and refrig spots and in the closet. The floor looks intentional and seems as though it has "always been there" this way.

I wanted to do that, but as long as the flooring guys shim everything to the proper height, it's fine. My wood is Owens Flooring - pre-engineered (with a nice thick "face" to it), so I don't need to worry about a site-finished job.